Magnetostatic wave filter

Abstract

A magnetostatic wave filter comprises a waveguide having a cut-off frequency region. In this waveguide, a YIG thin film is installed as a ferrimagnetic base material. Also, the cut-off frequency region of this waveguide comprises an attenuation band of the magnetostatic wave filter. Electromagnetic wave in the attenuation band of the magnetostatic wave filter is attenuated by this waveguide.

What is claimed is: 
     
       1. A magnetostatic wave filter comprising a waveguide having a given cut-off frequency, and terminating in at least one end in a region of cross sectional area greater than said waveguide;   a ferrimagnetic base material installed in said waveguide and extending for substantially the length thereof,   said ferrimagnetic base material having a main surface extending longitudinally of said waveguide;   whereby said cut-off frequency in said waveguide comprises an attenuation frequency.   
     
     
       2. A magnetostatic wave filter in accordance with claim 1, wherein said ferrimagnetic base material comprises a YIG thin film. 
     
     
       3. A magnetostatic wave filter in accordance with claim 2, which further comprises an input-side transducer connected to one end of said waveguide, and   an output-side transducer connected to the other end of said waveguide.   
     
     
       4. A magnetostatic wave filter in accordance with claim 3, wherein at least one of said input-side and output-side transducers is connected to said waveguide through another waveguide. 
     
     
       5. A magnetostatic wave filter in accordance with claim 4, wherein at least one of said input-side and output-side transducers comprises a box-shaped cover attached to said another waveguide,   a coaxial connector installed in a manner penetrating said cover, and   an antenna, one end of which is connected to the core conductor of said coaxial connector, and which is disposed in said cover.   
     
     
       6. A magnetostatic wave filter in accordance with claim 2, which further comprises a coaxial line connected to one end of said waveguide, and   another coaxial line connected to the other end of said waveguide.   
     
     
       7. A magnetostatic wave filter in accordance with claim 6, wherein said coaxial line comprises a block having a space part communicating with said wave guide,   a coaxial connector penetrating said block, and   a wire-shaped inner conductor disposed in the space part of said block, one end of which is connected to the core conductor of said coaxial connector, and the other end of which is connected to said block.   
     
     
       8. A magnetostatic wave filter comprising a waveguide having first and second sections in line with one another, and a third section intermediate said first and second sections, said third section having a transverse dimension less than said first and second sections, whereby said third section has a cut-off frequency lower than that of said first and second sections, and   a ferrimagnetic base material positioned in said third waveguide section,   wherein the third wave section in said waveguide comprises an attenuation region.